A magnetic recording media must have high output, particularly if they are audiocassette tapes used for recording music. More specifically, such tapes must have better frequency characteristics and better ability to reproduce recorded sound. Car stereos and radios with audiocassette recorders are getting very common and such devices promote the frequent use of such tapes. Accordingly, a tape having good running properties and durability is required.
In a videocassette tape recording system, recorded wave lengths are made shorter and the track width is made narrower to achieve a high density recording. Therefore, it is necessary for the tape to have a high output level and reproducing ability of an original image having a high S/N ratio. It is also necessary for a recording tape for a commercial video tape recorder (VTR) to have a thickness of about 20 .mu.m or thinner. The running property and durability of the tapes must be better than conventional video tapes due to the increased use of such tapes. Therefore, it is necessary to develope audio tapes and video tapes with better electromagnetic and running properties as well as increased durability.
Various additives have been proposed to improve these properties. However, none of the additives can completely satisfy all of the above requirements.
An example of one additive is a linear fatty acid which is obtained from animal or vegetable fats and oils, as described in U.S. Pat. Nos. 3,833,412 and 3,470,021. It is often used because it is cheap and provides good lubricating effects. However, these linear fatty acids such as linear saturated fatty acids (e.g., lauric acid, myristic acid or stearic acid) which are added to a magnetic recording layer are often separated from the layer and come out as a white powder on the surface of the magnetic recording layer. This separation occurs because they have a high boiling point and are easily crystallized. The white powder changes the output level and causes dropout. Further, linear unsaturated fatty acids (e.g., oleic acid or linolic acid) decrease the running property and durability of magnetic recording tapes with the passage of time. This happens because of oxidation with the passage of time. Furthermore, the use of such fatty acids does not provide sufficient running property at high temperature and high humidity.